An area for allowing a fluid to pass therethrough can be found in numerous contexts, and may be any area in a body for accommodating a flow of a fluid, or an opening serving as an inlet of a fluid, for letting in fluid to a place for receiving the fluid, an opening serving as an outlet of a fluid, for discharging fluid from a certain place, or an opening serving as a combination of an inlet and an outlet. In any case, such an area is in fact a passage for fluid, which may be delimited by material of one or more objects. For example, the area may be an opening at an end of a tube, or may be an opening in a wall delimiting a space for containing a fluid.
An example of a field in which the invention is well applicable is the field of water conditioning appliances for water cleaning, which can be used in a domestic environment for filtering water prior to reaching the faucet or as a terminal end device which may be mounted on the faucet. In general, one practical application of the invention is in the context of appliances which are adapted to treat water by means of mechanical filtration. Mechanical water filters are available in many types, and are of a porous nature, meaning that they comprise a filter body provided with apertures, the filter body representing a presence of material and having a function in retaining items to be removed from water, and the apertures representing an absence of material and having a function in allowing the water to pass the filter. Thus, when a flow of water is conducted through a mechanical water filter, items as may be present in the water at the inlet side of the filter get trapped in the filter and are prevented from reaching the outlet side of the filter, provided that they are not so small that they can pass through the apertures of the filter. A mechanical water filter may come in any form as suitable in a given situation. Practical examples include a disc provided with a pattern of holes, a collection of sand particles, a construction including interspaced strip-like elements, a piece of cotton cloth, and a block of dense but porous material such as ceramic.
In view of the function of filtering items from a fluid, it is normal for a filter to get clogged as time passes, which hinders the flow of fluid through the area in which the filter is present, and which may eventually result in total blockage of that area if the filter is not replaced or cleaned in time. In order to maintain the function of a filter at the highest possible level, it is desirable to remove factors which are known to contribute to clogging of the filter, as a result of which clogging takes place at an accelerated pace. A well-known example of such factors is a phenomenon called biological fouling or biofouling.
In general, biofouling is the accumulation of organisms like microorganisms, plants, algae, small animals and the like on surfaces. According to some estimates, over 1,800 species comprising over 4,000 organisms are responsible for biofouling. Hence, biofouling is caused by a wide variety of organisms. Biofouling is divided into micro biofouling which includes biofilm formation and bacterial adhesion, and macro biofouling which includes the attachment of larger organisms. Especially micro biofouling is an issue in the context of filters, and may cause significant shortening of the maintenance interval, especially in situations in which filters are applied for cleaning water or another fluid having a relatively high content of biofouling organisms.